The invention relates to a lighting device for optical and photooptical or photographic purposes, which device comprises an energy source, a light source and a housing with a transparent part with reflectors.
Devices as described above are known for viewing translucent media, such as for example slides, negatives, X-ray pictures or the like. In the process, the medium is placed on a transparent part on the surface of the device, which surface is usually plane and viewed with the aid of the lighting source. The reflectors in the transparent part ensure a uniform distribution of the light, so a larger, illuminated area is produced on the surface of the transparent part. In the known lighting devices, the lighting source is located behind the transparent part, reflectors being arranged on the side remote from the transparent part to reflect to the front the light radiated to the back. This results in relatively large or deep devices which are correspondingly unwieldy.
Devices of this type are, depending on size, transportable or rigidly integrated, for example into a table or a wall.
Light sources or lighting devices which should fully illuminate the object to be photographed, as far as possible without shadows, are used in photographic studios. Screen-like lighting devices are known for this purpose in which a lighting source is arranged in a focal point of a parabolic screen and the light is dispersed over as large an area as possible. These known lighting devices are also very bulky and cannot usually be placed close to the article to be photographed.
It is an object of the invention to provide an improved device of the type described above, in that it can be used for various applications and, in particular, is suitable for two-dimensional illumination when photographing.
To achieve this object, the invention starts from a lighting device as described above and proposes that, as a lighting source, a laterally arranged flash-lamp and/or normal lamp is provided which is arranged laterally in said housing next to said transparent part.
By virtue of the proposal according to the invention, a lighting device is produced which can be relatively narrow in design. It is therefore possible to use this device even in restricted spaces. It is also possible for said device to be relatively small in design, a plurality of said devices, for example, then being placed around the object to be illuminated to achieve optimum illumination of said article. The proposed design allows very compact construction of said illuminating device. As the illuminating devices according to the invention can be positioned relatively close to the objects to be illuminated (outside the visual range of the lens system, of course), it is also possible to work with smaller lighting sources, as not too much light disappears due to diffusion because of a large distance between said lighting source and said article to be illuminated. Adequate light intensity is nevertheless provided on the object to be illuminated. This also contributes to said lighting device being relatively small and neat in design, which significantly increases the range of application.
By using a flash-lamp in addition to, or in place of, a normal lamp, the lighting device can be used as a flash device, allowing illumination even of larger spaces due to the extensive distribution of the light. This significantly increases the versatility of said device.
In a preferred embodiment of the invention, said transparent part comprises a milk glass sheet, a parchment-like film and a transparent sheet, which preferably comprises plastics material. Said milk glass sheet or said parchment-like film allow a distribution of the light in the area of said transparent part which is as uniform as possible. It is the aim of said lighting device to produce a light intensity which is distributed as homogeneously and uniformly as possible over the area. The design of said transparent part contributes to this.
The transparent part is preferably substantially rectangular or square. This accords with the application as a viewing device for slides, X-ray pictures or the like. This shape has also proved successful for flat flash devices, as a radiation range which is as large as possible is thus produced.
For better distribution of the light, in a preferred embodiment of the invention reflective points are arranged on the underside of said transparent sheet, said reflective points forming a fine-meshed grid. The fact that the illumination does not appear close to the light source or the light sources means that optimum distribution of the light over the whole area of said transparent part is achieved and ensured. Said reflective points can be applied, for example, by screen printing, other processes also being conceivable. Additional reflective materials are not necessary in said reflective points.
It is also favourable if a reflective film is provided between the back wall of said housing and said reflective points. This reflective film is preferably held in a white plastics material and extends over the whole of the back of said transparent part.
Instead of the white paint or the white film for reflective points and reflective film, metallic or partially metallic material can also be used.
In the preferred embodiment of the invention, one or more flash-lamps and/or one or more normal lamps are arranged on one or more sides of said substantially rectangular or square, transparent parts, and the light produced by said light sources is enclosed in the lateral edge of said transparent sheet and owing to the reflection means arranged on the back of said sheet is radiated forwards.
Owing to the optional use of flash-lamps or normal lamps, if both lamps are built into the device, the lighting device can be used for a plurality of purposes by means of an appropriate circuit. For example, the flash-lamps can be arranged on two opposing sides of said square and the normal lamps on the two other opposing sides of said square. A corner arrangement is also possible. The light produced by the lighting sources falls laterally onto said transparent sheet and is reflected back by said reflective points or by the reflective film on the back of said sheet. Uniform distribution is achieved, on the one hand, by said parchment-like film and, on the other hand, by said covering milk glass sheet. It is achieved, owing to this arrangement that the light intensity is not substantially increased in comparison to the rest of the area, even at the side where the lamp is.
A better distribution of the light can also be achieved owing to a corresponding arrangement of the reflective points on the back.
To this end, it is favourable if the light source or the light sources are rod-shaped in design. A light rod of this type can include the whole side or edge of said transparent sheet, but a plurality of rod-shaped light sources can also be provided on one side. Both a normal lamp and a flash-lamp can, for example, be arranged on one side.
To increase the light output, reflectors can be arranged behind the light source. These reflectors are also a film or the like, which preferably consists of white material. Mirror-like metal films and similar can also be used here. The reflectors behind said light source shut off said light source as far as possible on all of the three sides which do not face the edge of said transparent sheet.
It has proved favourable where lamps are not provided on all of the edges of the plastic sheet, if light-proof seals or reflective layers are arranged on these edges. These layers reflect back the light and thus increase the light output. This also achieves a more uniform light distribution.
Owing to the cooperation of the various seals, reflective points and reflective films, an exceptionally uniform light distribution is achieved. The result is, in the case of the normal lamp, a uniformly illuminated milk glass sheet, which is excellent for viewing even awkward details on slides and the like. When flash-lamps are used, a extensive light emittance is achieved, which flash-lamps illuminate the object to be photographed very well and in comparison with conventional very small flash-lamps allow good photographs.
A further advantage of the device is that the thickness of the device is some mm to a few cm, and the housing is very narrow in relation to a side measurement of the housing. The thickness of said device forms an approximate ratio with the side measurement of said housing of a maximum of 1:5 to 1:10 (in small devices), and in large devices also a maximum of 1:20. This means that the result is a very flat device which is extremely easy to handle both in studio operation and in mobile operation. It is easy to accommodate and also correspondingly simple to combine with cameras and other photographic devices. The relatively narrow device is also ideally suited as a table-top device for viewing slides.
It is also favourable if a coupling is provided on the housing which corresponds to a tripod coupling. Couplings of this type are generally known and standardised, so that the device can be combined with any commercial tripod or also a camera.
In a preferred embodiment of the invention, a connection with an appropriate circuit is provided between the lighting device and a photooptical device, for example a camera. This circuit is used, in particular, if the device is to be used as a flashlight, so that the flash illuminates simultaneously when the camera is triggered. A circuit of this type can be integrated, for example, in the device.
Batteries or accumulators are preferably integrated into the device for the energy supply, but a connection can also be provided to an external power source. The variant with integrated batteries or accumulators is particularly suitable for mobile operation, while an external power source, for example a plug socket with a corresponding transformer, is suitable for studio operation.